// @file cpuprofile.cpp

/**
*    Copyright (C) 2012 10gen Inc.
*
*    This program is free software: you can redistribute it and/or  modify
*    it under the terms of the GNU Affero General Public License, version 3,
*    as published by the Free Software Foundation.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU Affero General Public License for more details.
*
*    You should have received a copy of the GNU Affero General Public License
*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*
*    As a special exception, the copyright holders give permission to link the
*    code of portions of this program with the OpenSSL library under certain
*    conditions as described in each individual source file and distribute
*    linked combinations including the program with the OpenSSL library. You
*    must comply with the GNU Affero General Public License in all respects for
*    all of the code used other than as permitted herein. If you modify file(s)
*    with this exception, you may extend this exception to your version of the
*    file(s), but you are not obligated to do so. If you do not wish to do so,
*    delete this exception statement from your version. If you delete this
*    exception statement from all source files in the program, then also delete
*    it in the license file.
*/

/**
 * This module provides commands for starting and stopping the Google perftools
 * cpu profiler linked into mongod.
 *
 * The following command enables the not-currently-enabled profiler, and writes
 * the profile data to the specified "profileFilename."
 *     { _cpuProfilerStart: { profileFilename: '/path/on/mongod-host.prof' } }
 *
 * The following command disables the already-enabled profiler:
 *     { _cpuProfilerStop: 1}
 *
 * The commands defined here, and profiling, are only available when enabled at
 * build-time with the "--use-cpu-profiler" argument to scons.
 *
 * Example SCons command line: 
 *
 *     scons --release --use-cpu-profiler 
 */

#include "gperftools/profiler.h"

#include <string>
#include <vector>

#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/authorization_manager.h"
#include "mongo/db/auth/privilege.h"
#include "mongo/db/client.h"
#include "mongo/db/commands.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/jsobj.h"

namespace mongo {

    namespace {

        /**
         * Common code for the implementation of cpu profiler commands.
         */
        class CpuProfilerCommand : public Command {
        public:
            CpuProfilerCommand( char const *name ) : Command( name ) {}
            virtual bool slaveOk() const { return true; }
            virtual bool adminOnly() const { return true; }
            virtual bool localHostOnlyIfNoAuth( const BSONObj& cmdObj ) { return true; }
            virtual void addRequiredPrivileges(const std::string& dbname,
                                               const BSONObj& cmdObj,
                                               std::vector<Privilege>* out) {
                ActionSet actions;
                actions.addAction(ActionType::cpuProfiler);
                out->push_back(Privilege(ResourcePattern::forClusterResource(), actions));
            }

            // This is an abuse of the global dbmutex.  We only really need to
            // ensure that only one cpuprofiler command runs at once; it would
            // be fine for it to run concurrently with other operations.
            virtual bool isWriteCommandForConfigServer() const { return true; }
        };

        /**
         * Class providing implementation of the _cpuProfilerStart command.
         */
        class CpuProfilerStartCommand : public CpuProfilerCommand {
        public:
            CpuProfilerStartCommand() : CpuProfilerCommand( commandName ) {}

            virtual bool run( OperationContext* txn,
                              std::string const &db,
                              BSONObj &cmdObj,
                              int options,
                              std::string &errmsg,
                              BSONObjBuilder &result);

            static char const *const commandName;
        } cpuProfilerStartCommandInstance;

        /**
         * Class providing implementation of the _cpuProfilerStop command.
         */
        class CpuProfilerStopCommand : public CpuProfilerCommand {
        public:
            CpuProfilerStopCommand() : CpuProfilerCommand( commandName ) {}

            virtual bool run( OperationContext* txn,
                              std::string const &db,
                              BSONObj &cmdObj,
                              int options,
                              std::string &errmsg,
                              BSONObjBuilder &result);

            static char const *const commandName;
        } cpuProfilerStopCommandInstance;

        char const *const CpuProfilerStartCommand::commandName = "_cpuProfilerStart";
        char const *const CpuProfilerStopCommand::commandName = "_cpuProfilerStop";

        bool CpuProfilerStartCommand::run( OperationContext* txn,
                                           std::string const &db,
                                           BSONObj &cmdObj,
                                           int options,
                                           std::string &errmsg,
                                           BSONObjBuilder &result) {
            ScopedTransaction transaction(txn, MODE_IX);
            Lock::DBLock dbXLock(txn->lockState(), db, MODE_X);
            // The lock here is just to prevent concurrency, nothing will write.
            OldClientContext ctx(txn, db);

            std::string profileFilename = cmdObj[commandName]["profileFilename"].String();
            if ( ! ::ProfilerStart( profileFilename.c_str() ) ) {
                errmsg = "Failed to start profiler";
                return false;
            }
            return true;
        }

        bool CpuProfilerStopCommand::run( OperationContext* txn,
                                          std::string const &db,
                                          BSONObj &cmdObj,
                                          int options,
                                          std::string &errmsg,
                                          BSONObjBuilder &result) {
            ScopedTransaction transaction(txn, MODE_IX);
            Lock::DBLock dbXLock(txn->lockState(), db, MODE_X);
            OldClientContext ctx(txn, db);

            ::ProfilerStop();
            return true;
        }

    }  // namespace

}  // namespace mongo